Does it do something to the board to close (kill button) the Serial Monitor?

If I close the Serial Monitor by clicking the trash-can kill icon, the on-board LED briefly flashes, and after I added the “onDisconnect” event handler of the TCP communication library I am using, I see the message that the TCP is disconnected.

This is odd, because I thought closing the Serial Monitor would do nothing to the board just as my turning off the television would not make any difference to the television station. Is it supposed to do something, or is this caused by something else (like a bug in my code)?